constructor()

in dotcom-rendering/cdk/lib/renderingStack.ts [176:292]

• 81 lines of code
• 3 McCabe index (conditional complexity)

	constructor(scope: CDKApp, id: string, props: RenderingCDKStackProps) {
		super(scope, id, {
			...props,
			// Any version of this app should run in the eu-west-1 region
			env: { region: 'eu-west-1' },
			// Set the stack within the constructor as this won't vary between apps
			stack: 'frontend',
		});

		const { stack: guStack, region, account } = this;
		const { guApp, stage, instanceType, scaling, domainName } = props;

		const artifactsBucket =
			GuDistributionBucketParameter.getInstance(this).valueAsString;

		const monitoringConfiguration =
			stage === 'PROD'
				? ({
						snsTopicName: `Frontend-${stage}-CriticalAlerts`,
						// TODO – how does this overlap with the DevX debug dashboard?
						http5xxAlarm: {
							tolerated5xxPercentage: 0.5, // Monitor and increase if too noisy
							numberOfMinutesAboveThresholdBeforeAlarm: 1,
						},
						unhealthyInstancesAlarm: true,
				  } satisfies Alarms)
				: ({ noMonitoring: true } satisfies NoMonitoring);

		const ec2App = new GuEc2App(this, {
			app: guApp,
			access: {
				// Restrict access to this range within the VPC
				cidrRanges: [Peer.ipv4('10.0.0.0/8')],
				scope: AccessScope.INTERNAL,
			},
			accessLogging: {
				enabled: true,
				prefix: `ELBLogs/${guStack}/${guApp}/${stage}`,
			},
			applicationLogging: {
				enabled: true,
				systemdUnitName: guApp,
			},
			// TODO - should we change to 3000?
			applicationPort: 9000,
			// Certificate is necessary for the creation of a listener on port 443,
			// instead of the default 8080 which is unreachable.
			certificateProps: { domainName },
			healthcheck: { path: '/_healthcheck' },
			instanceType,
			monitoringConfiguration,
			roleConfiguration: {
				additionalPolicies: [
					new GuAllowPolicy(this, 'AllowPolicyCloudwatchLogs', {
						actions: ['cloudwatch:*', 'logs:*'],
						resources: ['*'],
					}),
					new GuAllowPolicy(this, 'AllowPolicyDescribeDecryptKms', {
						actions: ['kms:Decrypt', 'kms:DescribeKey'],
						resources: [
							`arn:aws:kms:${region}:${account}:FrontendConfigKey`,
						],
					}),
					new GuAllowPolicy(this, 'AllowPolicyGetSsmParamsByPath', {
						actions: [
							'ssm:GetParametersByPath',
							'ssm:GetParameter',
						],
						resources: [
							// This is for backwards compatibility reasons with frontend apps and an old SSM naming system
							// TODO - ideally we should convert these params to use the newer naming style for consistency
							`arn:aws:ssm:${region}:${this.account}:parameter/frontend/*`,
							`arn:aws:ssm:${region}:${this.account}:parameter/dotcom/*`,
						],
					}),
				],
			},
			scaling,
			userData: getUserData({
				guApp,
				guStack,
				stage,
				artifactsBucket,
			}),
		});

		/**
		 * The default Node server keep alive timeout is 5 seconds
		 * @see https://nodejs.org/api/http.html#serverkeepalivetimeout
		 *
		 * This ensures that the load balancer idle timeout is less than the Node server keep alive timeout
		 * so that the Node app does not prematurely close the connection before the load balancer can accept the response.
		 * @see https://docs.aws.amazon.com/elasticloadbalancing/latest/application/application-load-balancers.html#connection-idle-timeout
		 */
		ec2App.loadBalancer.setAttribute('idle_timeout.timeout_seconds', '4');

		// Maps the certificate domain name to the load balancer DNS name
		new GuCname(this, 'LoadBalancerDNS', {
			domainName,
			app: guApp,
			resourceRecord: ec2App.loadBalancer.loadBalancerDnsName,
			ttl: Duration.hours(1),
		});

		/** Add CPU utilisation based STEP scaling policy for PROD only if a policy is defined */
		addCPUStepScalingPolicy(this, ec2App, props, stage);

		/** Add latency-based STEP scaling policy for PROD only if a policy is defined */
		addLatencyStepScalingPolicy(this, ec2App, props, stage);

		// Saves the value of the rendering base URL to SSM for frontend apps to use
		new StringParameter(this, 'RenderingBaseURLParam', {
			parameterName: `/${guStack}/${stage.toLowerCase()}/${guApp}.baseURL`,
			stringValue: `https://${domainName}`,
			description: `The rendering base URL for frontend to call the ${guApp} app in the ${stage} environment`,
		});
	}